数字跟字符串的转换

<?php
	$a =10;
	$b ="I is a string value";
	$e =$a+$b;
	$f =$b+$a;
	echo "automatic type conversions: <br>";
	echo '10+I is a string value='.$e."<br>";
	echo "force type conversions: <br>";
	echo '10+I is a string value='.(string)$e."<br>";
?><?php
	$a =10;
	$b ="I is a string value";
	$e